Method of making compressor or turbine rotor or stator blades

ABSTRACT

A METHOD OF MAKING AN ANNULUS OF BLADES FOR A GAS TURBINE ENGINE IS PROPOSED IN WHICH BLADE ROW IS FORMED FROM AN ANNULAR ARRAY OF PIECES, EACH COMPRISING A BLADE FLANK, AN INTERCONNECTING PORTION, AND AN OPPOSING FLANK OF AN ADJACENT BLADE. THE PIECES ARE MADE   FROM FIBER REINFORCED MATERIAL AND PREFERRED METHOD OF MANUFACTURE OF THE PIECES USING FILAMENT WINDING TECHNIQUES ARE UTILIZED IN MAKING THE INDIVIDUAL PIECES.

Nov. 2, 1971 I J. s. WALLETT 3,616,508

METHODOF MAKING COMPRESSOR OR TURBINE ROTOR OR STATOR BLADES Filed Jan.27, 1969 2 Sheets-Sheet 1 /0 /5 "V4 J| i\| &. x.

Invenlor J S. M441; T 7" Home ys Nov. 2, 1971 J. s. WALLETT 3,

METHOD OF MAKING COMPRESSOR 0R TURBINE ROTOR OR STATOR BLADES Filed Jan.27, 1969 2 Sheets-Sheet 2 I nvenlor I 5. Mum T?" B GwL/vma/w, (9111i 7(AAA) A llorneyg,

United States Patent Office 3,616,508 Patented Nov. 2, 1971 U.S. Cl.29156.8 R Claims ABSTRACT OF THE DISCLOSURE A method of making anannulus of blades for a gas turbine engine is proposed in which a bladerow is for-med from an annular array of pieces, each comprising a bladeflank, an interconnecting portion, and an opposing flank of an adjacentblade. The pieces are made from fiber reinforced material and preferredmethod of manufacture of the pieces using filament winding techniquesare utilized in making the individual pieces.

This invention relates to a method of making an annulus of blades for agas turbine engine.

There has recently been considerable interest in the use of compositematerials, particularly fibre re-inforced materials, for the manufactureof blades for gas turbine engines. The present invention provides amethod of making an annulus of blades from a fibre re-inforced materialwhich uses the high tensile strength of the fibre re-inforcement in anadvantageous fashion.

According to the present invention a method of making the annulus ofblades for a gas turbine engine from a fibre re-inforced materialcomprises the steps of: forming a plurality of pieces from the fibrere-inforced material, each piece comprising one aerodynamic flank of aportion of a blade, an interconnecting portion, and an opposingareodynamic flank of a portion of an adjacent blade; and fastening thepieces together in annular array so that each said blade flank of onepiece abuts an opposing blade flank on an adjacent piece to form acomplete blade.

According to another aspect of the present invention, a piece adaptedfor the method set out above comprises fibre re-inforced materialforming one aerodynamic flank of a blade, an interconnecting portion,and at least part of an opposing aerodynamic flank of an adjacent blade.

Preferably said pieces are so formed that the majority of the fibrere-enforcement in said blade flanks is aligned in a direction which issubstantially radial with respect to the assembled annular array.

When the pieces are assembled the interconnecting portion may be held ona blade disc by an axially extending beam piece which passes across andradially outside the interconnecting portion. The beam pieces may beheld by an axial nip between a pair of lipped disc portions.

In an alternative construction each piece comprises a box section memberin which opposing faces form the flank section while the remaining facesform inner and outer shroud members. In this case the portions may bejoined by adhering the flank portions together to form a completeannulus which may be joined to a disc.

In the latter case the portions are preferably formed by filamentwinding around a former whose external shape corresponds to theinter-blade shape required.

The invention will be particularly described merely by way of examplewith reference to the accompanying drawings in which:

FIG. 1 is a side elevation, partly broken away, of a gas turbine engineincorporating blades in accordance with the present invention;

FIG. 2 is a perspective view showing one embodiment of blades accordingto the present invention mounted on a disc;

FIG. 3 is a radial section in between two blades of the embodiment ofFIG. 2;

FIG. 4 is a perspective view of a further embodiment of the invention,and

FIG. 5 is a perspective view of a disc incorporating the blades of FIG.4.

In FIG. 1 there is shown a gas turbine engine comprising a compressor10, combustion equipment 11, turbine 12 and a final nozzle 13. Thecasing of the compressor 10 is broken away at its left hand extremity toshow compressor rotor blades 14 and stator blades 15.

FIG. 2 shows in perspective the compressor blades 14 together with theirmounting arrangements on a compressor disc, part of which is shown at16. The blades 14 are made up from a series of U shaped pieces, eachbeing formed from a fibre re-inforced resin material and comprising anaerodynamic flank portion 17 of concave transverse section a U shapedinterconnecting portion 18 and an aerodynamic flank portion 19 of convextransverse section. It will be seen that the pieces are of generally Ushaped overall, the limbs of the U shape forming the aerodynamic flankportions 17 and 19 while the remainder forms the interconnecting portion18. Each portion 17 is glued to the portion 19 of the next adjacentpiece so as to form a complete blade 14, and it will be appreciated thatthe U shaped pieces together form a complete annular array of blades 14.

Each of the U shaped pieces is held in position on the disc 16 by virtueof the engagement of a half cylindrical beam member 20 with theinterconnecting portion 18. As can be seen best in FIG. 3 the beammember 20 extends axially in between two retaining disc portions 21 and22. It will be evident that the blades are thus held against centrifugalloads by tensile stresses in the portion 18 which are transferred to thebeam 20 and hence to the disc 22, while bending moments may be reactedinto the beam portions 20 by glueing the portions 20 to the portions 18.If required the interconnecting portions 18 may also be glued to themain disc 16 so as to provide further strength against bending.

In order to smooth the root shroud portion of the blades 14 the centralchannel in each of the beam por tions 20 is filled as shown at 23 by alightweight foamed plastic filler which provides a smooth externalsurface.

In each of the U shaped portions made up of the flanks 17 and 19 and theinterconnecting portion 18 the fibre re-inforcements are arranged to runradially of the disc 16 in the flanks 17 and 19 and to follow the lineof the interconnecting portion 18 so that they are substantiallycircumferentially disposed in this portion. It will be appreciated thatusing this construction the fibres are arranged to be under tension byvirtue of the centrifugal loads on the blades; since it is in tension inwhich these re-inforcement fibres, which may for instance be carbon orgraphite fibres, are strongest it will be appreciated that this methodis an advantageous way of making and mounting blades. The fibresreferred to in the above example may conveniently be laid up to form theU shaped pieces as continuous filaments in a filament winding techinque.

FIG. 4 shows in perspective a further way of manufacturing bladesaccording to the present invention. A former'25 is provided part ofwhose surfaces are formed to be in the shape of the space required inbetween two blades 14, and coated with a parting agent if necessary.Around these surfaces re-inforcing fibre in the form of a continuousfilament having a coating of resin which is allowed to become tacky iswound as indicated at 2-6 and 27. The winding may conveniently beeffected by rotating the former about a central axis (indicated at AA)while feeding the filament into the correct position. It is necessarythat the filament be tacky to enable the filament to remain in place onsurface areas of high slope. Once the filament has been wound aroundthese surfaces, it is further impregnated with resin and the whole isheated to cure the resin. The former 25 is split as shown at 28 and 29into three pieces, one of which is wedge shaped and can easily bewithdrawn from inside the cured number 30.

It will therefore be appreciated that this wedge shaped portion can beremoved and leaves space for the remaining portions of the former 25 tobe removed; leaving the portion 30. The portion 30 thus takes the formof a hollow box open at opposed faces and having an inner shape which isthe required shape of the inter-blade spac ing. The portion which wasagainst the wall 26 becomes a convex flank (equivalent to 19) and theopposing sur- FIG. 5 is a perspective view of a disc 16 from which aremounted a plurality of blades 14 and which indicates how the box sectionmembers 30 are used to form an annulus of blades. In the lower portionof FIG. 5 the blades 14 are made up of box sections 30 as shown in FIG.4 and it will be noted that each 'box section abuts against an adjacentbox section so that the two flank portions abut to form a single hollowblade 14. In this case the outer shroud portions have been left inposition and form a continuous outer shroud as indicated at 31. Theinner shroud portions of the box sections are connected to the disc 16at 32 by means of a resin bonding technique.

It will be appreciated that were it required to manufacture a row ofstator blades, then it would be unnecessary to stick the box sections at32; instead it might be required for instance to stick the portions 31to a casing of the engine.

The upper part of FIG. 5 shows a slightly different way of using the boxsections 30. In this case the outer shroud portions have been cut off,leaving the portions having a rectangular U shape. These portions may beused in a similar fashion to those shown in FIG. 2; as an alternativethey may be simply glued to the disc 16 as shown at 33. Again it wouldbe appreciated that the fibres forming the blade 14 are in tension Whencentrifugal loading is present, this being the strongest direction ofthe fibre re-inforcement.

Although this is not illustrated it would of course be possible to cutaway the inner shroud portions of the box section members 30; this mightbe necessary where it is proposed to manufacture the stator bladeshaving no could be used in other matrix materials such as nickel matrixwhich would be useful where high temperatures are to be experienced;alternatively different fibre materials such as boron or silica can beused in matrix materials such as aluminium.

It will also be appreciated that although the embodiments illustratedprovide a complete flank on each of the limbs of the U section, it wouldbe possible to provide merely a portion of the flank on one limb, theremainder of this flank being provided on the abutting limb of the nextadjacent portion.

The above embodiments comprise hollow blades; the technique of thepresent invention can thus be seen to enable the production of hollowblades relatively easily. The advantages of hollow blades are of coursewell known.

I claim:

1. A method of making an annulus of blades for a gas turbine engine froma fibre reinforced material comprising the steps of: forming a pluralityof similar pieces from the fibre reinforced material, each piececomprising one aerodynamic flank of a portion of a blade, aninterconnecting portion, and an opposing aerodynamic flank of a portionof an adjacent blade; and fastening the pieces together in annular arrayso that one said blade flank of one piece abuts the opposing flank on anadjacent piece to form a complete blade.

2. A method of making an annulus of blades as claimed in claim 1 and inwhich said pieces are so formed that the majority of the fibrere-inforcement in said blade flanks is aligned in a direction which issubstantially radial with respect to the assembled annular array.

3. A method of making an annulus of blades as claimed in claim 2 inwhich said pieces are made by filament winding the fibre reinforcementon a former, said former having the shape of the required inter-bladespacing in the annular array, so as to form one aerodynamic flank with aconcave portion and the opposing aerodynamic flank with a convex portionand interconnecting inner and outer shrouds.

4. A method of making an annulus of blades as claimed in claim 3 andcomprising the additional step of removing one said shroud from eachsaid piece whereby an annular array is produced whose blades areunshrouded at one end.

5. A method of making an annulus of blades as claimed in claim 1 and inwhich said fibre comprises carbon fibre.

References Cited UNITED STATES PATENTS 2,649,243 8/1953 Stalker 4l5l942,786,646 3/1957 Grantham 4l62l3 X 3,403,844 10/1968 Stoffer 4l62303,424,434 1/1969 Palfreyman et al. 416-230 JOHN F. CAMPBELL, PrimaryExaminer V. A. DI PALMA, Assistant Examiner U.S. Cl. X.R. 4l62l3, 217,230

